Objective: The aim of this study was to demonstrate inflammatory effects on soft and hard tissues of palate and nasal mucosa after insertion of orthodontic mini-implants (MI).
Methods: Twenty-four Wistar rats were used in this study. Each animal received 4 MIs on palate, parallel to the palatine suture, simulating a maxillary expansion supported by mini-implants. Titanium grade V mini-implants with1.5x5.5mm and 1.5x3.0mm were used in each animal and evaluated on days 2, 7, 14 and 28. The MIs were divided according to insertion depth: 1- insertion only in bone tissue; 2- MI tip invade nasal mucosa and 3- MI penetrate nasal cavity. Number of inflammatory cells, tissue thickness (epithelial thickness index - ETI and subepithelial thickness index - STI) and MI stability were evaluated over time.
Results: The number of inflammatory cells showed higher proliferation after 7 days, tending to a reduction over time in all groups. The ETI was similar for all groups through time. On the other hand, STI was higher in the group whose MI invaded nasal mucosa at day 2 compared to other groups and higher when MI penetrated nasal cavity at days 7 and 14. Regardless of the group or condition, all mini-implants were stable during the entire experiment.
Conclusion: Change of the nasal tissue occurred in the three cases, with less intensity when MI was inserted only in bone which suggests the adoption of post-surgical care when palate’s MI are in close contact with nasal mucosa or inserted into nasal cavity.